Project Summary/Abstract The NICHD has identified bullying as a significant public health concern and, through the Social and Emotional Development/Child and Family Process Program, supports research on the processes that contribute to, or discourage, bullying among youth. The research proposed here will test a novel approach to increase children?s defending of victims of bullying. Previous research has shown that the presence of defenders leads to decreases in bullying. Thus, promoting defending has become a critical component of anti-bullying interventions. However, how to best motivate defending has been relatively unstudied. Deviance Regulation Theory (DRT) provides a theoretical basis for motivating positive health and social behaviors. This theory proposes that individuals are motivated to behave in ways that differentiate them from others in a positive manner. Accordingly, individuals will be motivated to engage in a behavior if they believe the behavior occurs infrequently and will be viewed positively by others. As children report that few of their peers defend victims of bullying, the goal of this study is to increase defending by communicating to children that defenders possess traits valued by their peers (e.g., being popular, kind). Children in 4th-grade and 5th-grade classrooms will receive a DRT- based anti-bullying intervention or an anti-bullying intervention focused on increasing empathy for victims and strategies for defending peers. Data collection will occur three times during the school year: a) at baseline, two weeks prior to the intervention; b) 3 months post-intervention; and c) 6 months post-intervention. Findings will show whether, compared to the traditional anti- bullying intervention, the DRT-based intervention results in larger, more sustained gains in defending. The study will also examine whether gains in defending are greatest among children who have low perceived norms for defending and, therefore, would otherwise be the least likely to stand up for victims. Other factors that may increase the efficacy of the intervention will be examined, including children?s gender, popularity, past peer victimization, empathy, moral disengagement, and self-efficacy for defending. This study will also examine whether the DRT- based intervention leads to decreases in aggression and victimization by increasing classroom- levels of defending. This study supports the mission of the NICHD by contributing to our understanding of the motivational processes underlying defending. The findings will have implications for the development of anti-bullying interventions and more broadly for understanding how to encourage important behavioral changes in childhood and adolescence.